Flutter was sold as accepting up to 16 Volts input on the Basic and 24 Volts input on the Pro. The regulators can accept these voltages, but it was discovered that voltages above 7 Volts may damage the battery charger circuit.

IF YOU HOOK UP MORE THAN 7 VOLTS TO THE "RAW" INPUT, IT MAY DESTROY THE BATTERY CHARGER. It will not affect the rest of the board's operation.

We recommend powering Flutter via USB when possible, as it is easy and avoids potentially damaging the battery charger. However, many of you may want to use the full voltage input range advertised to power your board, so we've included one "7805" Five Volt regulator for each board shipped. If you want to run Flutter off of a voltage higher than 7 volts, hook that voltage up to the input of the 7805 regulator, and hook the output of the regulator up to Flutter's RAW input

Full instructions will be added to this page in the future, but for now please see this link for more information.

Good question. I believe it was mentioned in one of the updates maybe 18 months ago, but all Flutter boards (Basic and Pro) get the charger. It makes it easier to have a consistent experience with accessories when both boards have the charger circuit.